Generally, a compressor can be formed by various types according to compressing methods, and as an air conditioning apparatus which is required to be smaller and lighter, a hermetic rotary compressor is mainly used.
FIG. 1 is a transverse sectional view showing a hermetic compressor in accordance with the conventional art, and FIG. 2 is a longitudinal sectional view showing a compressing unit of the hermetic compressor in accordance with the conventional art.
A hermetic rotary compressor in accordance with the conventional art includes a case 106 having a hermetic space therein, which is connected with a suction tube 102 to which gas is sucked and a discharge tube 104 through which compressed gas is discharged, a driving unit 108 which is mounted at an upper portion of the case 106, for generating a driving force, a compressing unit 112 which is connected with the driving unit 108 with a rotational shaft 110, for compressing fluid by a rotational force generated in the driving unit 108.
The driving unit 108 includes a stator 114 which is fixed on the inner circumference of the case 106 and to which a power is applied from the outside, and a rotor 116 which is positioned on the inner circumference of the stator 114 at a predetermined interval from the stator 114, and rotates by interaction with the stator 114 when a power is applied to the stator 114.
The compressing unit 112 includes an eccentric portion 118 which is at a lower portion of the rotational shaft 110 fixed on the inner circumferential surface of the rotor 116, a cylinder 120 in which the eccentric portion 118 is inserted and gas is compressed and which is fixed on the case 106, upper and lower frames 122 and 124 which are combined with the upper and lower side of the cylinder 120 so as to seal the compressing space of the cylinder 120, for rotably supporting the rotational shaft 110, a piston 128 which is inserted in the circumferential surface of the eccentric portion 118 of the rotational shaft 110, for compressing fluid while revolving the compressing space 126 of the cylinder 120, and a vane 130 which is inserted at a side of the compressing space 126 of the cylinder in the radius direction so that it can perform linear movement and is linearly contacted on the outer circumferential surface of the piston 128, for dividing the compressing space 126 of the cylinder 120 into a suction region 126a and compressing region 126b. 
A suction port 132 which is connected with the suction tube 102 to suck gas is formed on a side surface of the suction region 126a in the compressing space 126, and a discharge port 134 through which gas compressed in the compressing space 126 is discharged is formed on the upper surface of the compressing region 126b. 
A discharge hole 136 which is connected with the discharge port 134 is formed in the upper frame 122, and discharges the gas discharged through the discharge port 134 in the upward direction of the case 106. In addition, a check valve 140 for preventing inverse flow of gas to the compressing space 126 is mounted on the upper surface of the discharge hole 136.
The vane 130 is inserted in an insertion hole 142 formed in the cylinder 120 so that it can perform linear movement, and a coil spring 144 is positioned between the vane 130 and the insertion hole 142 so as to be elastically abutted on the outer circumferential surface of the piston 128.
The suction tube 102 is connected with an accumulator 150 for preventing inflow of liquid refrigerant, and the accumulator 150 is connected with an evaporator which composes a freezing cycle.
The operation of the conventional hermetic compressor with the above structure will be described.
When a power is applied to the stator 114 of the driving unit 108, the rotor 116 rotates by interaction between the stator 114 and the rotor 116 and the rotational shaft 110 rotates together. Then, the eccentric portion 118 which is mounted at a lower end of the rotational shaft 110 rotates, and the rolling piston 128 which is mounted in the circumferential direction of the eccentric portion 118 revolves in the compression space under an eccentric condition.
At this time, the gas which flows to the suction tube 102 is sucked to the compression space 126 of the cylinder 120 through the suction port 132, and low temperature and low pressure gas is compressed to high temperature and high pressure gas by change of volume of the compressing space 126 caused by revolution of the rolling piston 128. Therefore, the high temperature and high pressure gas is discharged into the case 106 through the discharge port 134 and the discharge hole 136.
The high temperature and high pressure gas discharged into the case 106 flows through a space between the stator 114 and rotor 116 of the driving unit 108 and a space between inner walls of the stator 114 and rotor 116 and is discharged to the outside through the discharge tube 104.
However, in the above described conventional hermetic compressor, since gas is sucked to the compressing space of the cylinder through the suction tube, is compressed by revolution of the rolling piston, and is discharged to the discharge tube by passing the inside of the case, high temperature and high pressure gas passes the inside of the case, and accordingly, the case must be designed by considering different internal pressures according to the pressure of gas. Therefore, the thickness of the case becomes thicker and manufacturing cost is increased by reinforcing the strength of the case.
Also, since the high temperature and high pressure gas passes between the stator and rotor of the driving unit, temperature of the driving unit increases and performance of the driving unit is degraded.
Also, since the high temperature and high pressure gas causes pressure loss by increased flow resistance of the gas and passes the inside of the case, noise was increased by pressure pulsation caused by difference of internal volume of the case.